S-Glutathionylation regulates HDL-associated paraoxonase 1 (PON1) activity

Salvia officinalis Improves Glycemia and Suppresses Pro-inflammatory Features in Obese Rats with Metabolic Syndrome

OBJECTIVES

Obesity is regarded as the main cause of metabolic diseases and a core factor for all-cause mortality in the general population, notably from cardiovascular disease. The majority of people with type 2 diabetes have obesity and insulin resistance. Some evidence indicates that an individual with obesity is approximately 10 times more likely to develop type 2 diabetes than someone with moderate body weight. One of the most significant therapeutic herbs, Salvia officinalis (Lamiaceae) (SAGE), possesses potent medicinal importance. The aim of this article was to evaluate the anti-diabetic and antiobesity activity of SAGEAE against HFD-induced obesity in rats.

METHODS

Thirty adult albino rats were randomly divided into five equal groups: control, High-fat Diet (HFD) administrated rats, HFD + Salvia officinalis Aqueous Extract (SAGEAE) (150 mg/kg.bw.), HFD + SAGEAE (300 mg/kg.bw.) and HFD + metformin (500 mg/kg.bw.). Body weight, plasma biochemical parameters, oxidative stress, inflammatory indicators, hepatic Phosphoenolpyruvate Carboxykinase 1 (PCK1), Glucokinase (GK), brain Leptin Receptor (LepRb), Glucose Transporter-4 (GLUT4), Sirtuin 1 (SIRT1) and mRNA33-5P gene signalling mRNA levels were all assessed after 8 weeks. A histological examination of the liver was also performed to check for lipid accumulation.

RESULTS

The administration of HFD resulted in increased body weight, glucose, insulin, leptin, Total Cholesterol (TC), Triglycerides (TG), Thiobarbaturic Acid Reactive Substances (TBARS), Monocyte Chemoattractant Protein-1 (MCP1), Interleukine-6 (IL-6) and tumor necrosis factor-α (TNF- α) as well as hepatic PCK1, brain LepRb and adipose tissue mRNA33-5P gene expression. However, our findings revealed a significant reduction in adiponectin, High-density Lipoproteincholesterol (HDL-C), reduced glutathione (GSH) and Superoxide Dismutase (SOD) levels as well as the expression of hepatic GK and adipose tissue SIRT1 and GLUT4 genes. Also, administration of SAGEAE significantly normalized body weight, glucose, insulin, leptin, adiponectin, TC, TG, HDL-C, TBARs, SOD, IL-6, MCP-1 and TNF-α in plasma and liver tissue of HFD-treated rats. On the other hand, PCK1, GK, LepRb, SIRT1, GLUT4 and mRNA33-5P gene expression was enhanced in obese rats when administrated with SAGEAE. Histological and US studies support the biochemical, PCR and electrophoretic results.

CONCLUSION

The findings imply that SAGEAE could be used as a new pharmaceutical formula in the treatment of obesity.

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

Paraoxonase-1: How a xenobiotic detoxifying enzyme has become an actor in the pathophysiology of infectious diseases and cancer

Both infectious and non-infectious diseases can share common molecular mechanisms, including oxidative stress and inflammation. External factors, such as bacterial or viral infections, excessive calorie intake, inadequate nutrients, or environmental factors, can cause metabolic disorders, resulting in an imbalance between free radical production and natural antioxidant systems. These factors may lead to the production of free radicals that can oxidize lipids, proteins, and nucleic acids, causing metabolic alterations that influence the pathogenesis of the disease. The relationship between oxidation and inflammation is crucial, as they both contribute to the development of cellular pathology. Paraoxonase 1 (PON1) is a vital enzyme in regulating these processes. PON1 is an enzyme that is bound to high-density lipoproteins and protects the organism against oxidative stress and toxic substances. It breaks down lipid peroxides in lipoproteins and cells, enhances the protection of high-density lipoproteins against different infectious agents, and is a critical component of the innate immune system. Impaired PON1 function can affect cellular homeostasis pathways and cause metabolically driven chronic inflammatory states. Therefore, understanding these relationships can help to improve treatments and identify new therapeutic targets. This review also examines the advantages and disadvantages of measuring serum PON1 levels in clinical settings, providing insight into the potential clinical use of this enzyme.

Overweight and obesity in polycystic ovary syndrome: association with inflammation, oxidative stress and dyslipidaemia

Polycystic ovary syndrome (PCOS) is associated with altered lipid profile and increased small, dense LDL particles (sdLDL). Considering that paraoxonase 1 (PON1) is an antioxidative enzyme located on HDL particles, the aim of this study was to investigate the connection between oxidative stress (OS) and PON1 activity with lipoprotein subclasses in PCOS depending on obesity. In 115 PCOS patients, lipoprotein subclasses distributions were determined by gradient gel electrophoresis. OS status was assessed by total oxidative status (TOS), advanced oxidation protein products, malondialdehyde (MDA), prooxidant-antioxidant balance (PAB), total antioxidative status (TAS) and superoxide dismutase (SOD) and PON1 activity. Overweight/obese PCOS patients (n 55) had increased OS compared with normal weight patients (n 60). In addition, overweight/obese group had lower HDL size and higher proportion of HDL 3a subclasses (P < 0·05). PAB was in negative correlation with HDL 2a (P < 0·001), whereas MDA and SOD correlated positively with HDL 3 subclasses (P < 0·05). Serum PON1 activity was positively associated with proportions of PON1 activity on HDL 2b (P < 0·05) and 2a (P < 0·01), but negatively with the proportion on HDL 3 particles (P < 0·01). LDL B phenotype patients had increased TAS, SOD and PON1 activity on HDL 2b, but decreased PON1 activity on HDL 3 subclasses. OS is associated with altered lipoprotein subclasses distribution in PCOS patients. Obesity in PCOS affects the profile of HDL subclasses, reflected through the reduced proportion of PON1 activity on HDL 3 subclasses in the presence of sdLDL particles.

Thiol Modifications in the Extracellular Space—Key Proteins in Inflammation and Viral Infection

Posttranslational modifications (PTMs) allow to control molecular and cellular functions in response to specific signals and changes in the microenvironment of cells. They regulate structure, localization, stability, and function of proteins in a spatial and temporal manner. Among them, specific thiol modifications of cysteine (Cys) residues facilitate rapid signal transduction. In fact, Cys is unique because it contains the highly reactive thiol group that can undergo different reversible and irreversible modifications. Upon inflammation and changes in the cellular microenvironment, many extracellular soluble and membrane proteins undergo thiol modifications, particularly dithiol–disulfide exchange, S-glutathionylation, and S-nitrosylation. Among others, these thiol switches are essential for inflammatory signaling, regulation of gene expression, cytokine release, immunoglobulin function and isoform variation, and antigen presentation. Interestingly, also the redox state of bacterial and viral proteins depends on host cell-mediated redox reactions that are critical for invasion and infection. Here, we highlight mechanistic thiol switches in inflammatory pathways and infections including cholera, diphtheria, hepatitis, human immunodeficiency virus (HIV), influenza, and coronavirus disease 2019 (COVID-19).

Human Paraoxonase-2 (PON2): Protein Functions and Modulation

PON1, PON2, and PON3 belong to a family of lactone hydrolyzing enzymes endowed with various substrate specificities. Among PONs, PON2 shows the highest hydrolytic activity toward many acyl-homoserine lactones (acyl-HL) involved in bacterial quorum-sensing signaling. Accordingly, defense against pathogens, such as Brevundimonas aeruginosa (B. aeruginosa), was postulated to be the principal function of PON2. However, recent findings have highlighted the importance of PON2 in oxidative stress control, inhibition of apoptosis, and the progression of various types of malignancies. This review focuses on all of these aspects of PON2.

Paraoxonase 1 and atherosclerosis-related diseases

A direct and an indirect relationship between paraoxonase 1 (PON1) and atherosclerosis exists. Given PON1's physical location within high-density lipoprotein (HDL) particles and its recognized enzyme activity, it is certainly reasonable to suggest that PON1 facilitates the antiatherogenic nature of HDL particles. PON1 also plays a role in regulating reverse cholesterol transport, antioxidative, anti-inflammatory, antiapoptotic, vasodilative, and antithrombotic activities and several endothelial cell functions. HDL dysfunctionality is a more recent issue and seems to be centered on pathological conditions affecting HDL structure and size profiles. This review is focused on the role of PON1 status in different atherosclerosis-related diseases that we have studied over the last twenty years (coronary heart disease, acute ischemic stroke, diabetes mellitus type 2, end-stage renal disease, chronic obstructive pulmonary disease, and sarcoidosis) with the aim to determine the true value of PON1 as a biomarker. The role of PON1 in cancer is also covered, as risk factors and mechanisms underlying both atherosclerosis and cancer share common features.

Enzymatic Bioremediation of Organophosphate Compounds-Progress and Remaining Challenges

Organophosphate compounds are ubiquitously employed as agricultural pesticides and maintained as chemical warfare agents by several nations. These compounds are highly toxic, show environmental persistence and accumulation, and contribute to numerous cases of poisoning and death each year. While their use as weapons of mass destruction is rare, these never fully disappear into obscurity as they continue to be tools of fear and control by governments and terrorist organizations. Beyond weaponization, their wide-scale dissemination as agricultural products has led to environmental accumulation and intoxication of soil and water across the globe. Therefore, there is a dire need for rapid and safe agents for environmental bioremediation, personal decontamination, and as therapeutic detoxicants. Organophosphate hydrolyzing enzymes are emerging as appealing targets to satisfy decontamination needs owing to their ability to hydrolyze both pesticides and nerve agents using biologically-derived materials safe for both the environment and the individual. As the release of genetically modified organisms is not widely accepted practice, researchers are exploring alternative strategies of organophosphate bioremediation that focus on cell-free enzyme systems. In this review, we first discuss several of the more prevalent organophosphorus hydrolyzing enzymes along with research and engineering efforts that have led to an enhancement in their activity, substrate tolerance, and stability. In the later half we focus on advances achieved through research focusing on enhancing the catalytic activity and stability of phosphotriesterase, a model organophosphate hydrolase, using various approaches such as nanoparticle display, DNA scaffolding, and outer membrane vesicle encapsulation.

Protein S-Glutathionylation Mediates Macrophage Responses to Metabolic Cues from the Extracellular Environment

AIMS

Protein S-glutathionylation, the formation of a mixed disulfide between glutathione and protein thiols, is an oxidative modification that has emerged as a new signaling paradigm, potentially linking oxidative stress to chronic inflammation associated with heart disease, diabetes, cancer, lung disease, and aging. Using a novel, highly sensitive, and selective proteomic approach to identify S-glutathionylated proteins, we tested the hypothesis that monocytes and macrophages sense changes in their microenvironment and respond to metabolic stress by altering their protein thiol S-glutathionylation status.

RESULTS

We identified over 130 S-glutathionylated proteins, which were associated with a variety of cellular functions, including metabolism, transcription and translation, protein folding, free radical scavenging, cell motility, and cell death. Over 90% of S-glutathionylated proteins identified in metabolically stressed THP-1 monocytes were also found in hydrogen peroxide (H₂O₂)-treated cells, suggesting that H₂O₂ mediates metabolic stress-induced protein S-glutathionylation in monocytes and macrophages. We validated our findings in mouse peritoneal macrophages isolated from both healthy and dyslipidemic atherosclerotic mice and found that 52% of the S-glutathionylated proteins found in THP-1 monocytes were also identified in vivo. Changes in macrophage protein S-glutathionylation induced by dyslipidemia were sexually dimorphic.

INNOVATION

We provide a novel mechanistic link between metabolic (and thiol oxidative) stress, macrophage dysfunction, and chronic inflammatory diseases associated with metabolic disorders.

CONCLUSION

Our data support the concept that changes in the extracellular metabolic microenvironment induce S-glutathionylation of proteins central to macrophage metabolism and a wide array of cellular signaling pathways and functions, which in turn initiate and promote functional and phenotypic changes in macrophages. Antioxid. Redox Signal. 25, 836-851.

Changes in the anti-oxidant system in adult epilepsy patients receiving anti-epileptic drugs

Anti-epileptic drugs (AEDs) have been widely used in patients with epilepsy. This study evaluated the adverse effects of two commonly prescribed AED monotherapies, carbamazepine (CBZ) and valproic acid (VPA). The aim of this study was to evaluate the influence of these anti-epileptic drugs on paraoxonase-1 (PON-1), glutathione S-transferase (GST) and acetyl cholinesterase (AChE) activities in the serum of adult patients with epilepsy. Of the 56 epileptic adults, 28 were given valproate, and the remaining 28 were given carbamazepine. Glutathione (GSH) levels in epilepsy patients receiving anti-epileptic drug treatment were insignificantly higher compared with controls. GST activity in epilepsy patients receiving anti-epileptic drug treatment was insignificantly lower compared with controls. PON1 and AChE activity in epilepsy patients receiving anti-epileptic drug treatment was significantly lower compared with controls. PON1 and AChE activities in the serum of patients treated with carbamazepine monotherapy were lower than in patients treated with valproic acid monotherapy.

Paraoxonases function as unique protectors against cardiovascular diseases and diabetes: Updated experimental and clinical data

Paraoxonase (PON) refers to a family of three enzymes, namely PON1, PON2, and PON3. PON1 and PON3 are found in circulation bound to high-density lipoprotein, whereas PON2 is an intracellular protein. PON1 was first discovered as an enzyme to hydrolyze the organophosphate pesticide paraoxon, an activity that both PON2 and PON3 lack. All three PON enzymes are able to degrade oxidized lipids and protect against oxidative stress. PON enzymes also act to suppress inflammation. Animal studies show a critical role for PON enzymes, especially PON1 in protecting against cardiovascular diseases and related disorders, including diabetes and metabolic syndrome. In line with the findings in experimental animals, accumulating evidence from clinical research also indicates that PON enzymes function as potential protectors in human cardiovascular diseases and related disorders. Identification of PON enzymes as important players in cardiovascular health will facilitate the development of novel preventive and therapeutic modalities targeting PON enzymes to combat cardiovascular diseases and related disorders, which collectively constitute the chief contributors to the global burden of disease. This review describes the biochemical properties and molecular regulation of PON and summarizes the major recent findings on the functions of PON in protecting against cardiovascular diseases and related disorders.

Plasma paraoxonase 1 arylesterase activity in D-galactose-induced aged rat model: correlation with LDL oxidation and redox status

OBJECTIVE

There is much evidence linking the involvement of oxidative stress in the pathogenesis of aging. Paraoxonase 1 (PON1) is an HDL-associated antioxidant enzyme that inhibits the oxidative modification of low-density lipoproteins (LDL). We have investigated the changes in plasma PON1 activity, LDL oxidation, radical scavenging activity and lipid peroxidation in D-galactose-induced aging rat model and also compared the results with 24-month naturally aged rats.

METHOD

Arylesterase activity of PON1, susceptibility of LDL for oxidation, plasma radical scavenging activity and plasma thiobarbituric acid reactive substances (TBARS) were measured in normal control rats (4-months-old control rats subjected to D-galactose-induced experimental aging, and 24-month-old naturally aged rats).

RESULTS

There was a significant decrease in plasma PON1 arylesterase activity in both subcutaneous D-galactose-treated groups and 24-month-old aged rats (P < 0.05, for each). TBARS, an oxidative stress marker, was seen to increase in the experimental groups (P < 0.01). In both subcutaneous galactose-treated and naturally aged rats, there was a significant rise in plasma LDL oxidation (P < 0.05, for each). However, radical scavenging activity was decreased significantly (P < 0.01) in both groups, as compared to control.

CONCLUSIONS

The D-galactose-induced rat model of aging mimics the naturally aged rat with reference to PON1 arylesterase activity and susceptibility to LDL oxidation. The results emphasize the importance of PON1 with respect to aging and its association with redox balance of the body.

Paraoxonase 1 activities, regulation, and interactions with atherosclerotic lesion

PURPOSE OF REVIEW

Improving serum levels of HDL and its subfractions, as well as, oxidative/inflammatory properties has become a fundamental aim in today's atherosclerosis research. Efforts to reach this goal are paralleled by achievements in drug development toward decreasing serum LDL levels and oxidative status.

RECENT FINDINGS

Paraoxonase1 (PON1) is an HDL-associated enzyme that is deemed responsible for many of the HDL's antiatherogenic and cardioprotective characteristics. PON1 is highly sensitive to variations in its milieu, and endogenous compounds (fatty acids, phospholipids), nutritional ingredients (flavonoids and other antioxidants), and environmental elements (reactive nitrogen and oxygen species, metals, surfactants), significantly affect the enzyme's activities. PON1 was shown to be responsible for some of the HDL antiatherogenic characteristics such as HDL-mediated cholesterol efflux from macrophages, and the inhibition of LDL oxidation.

SUMMARY

The present review summarizes the recent literature related to various elements in PON1's milieu that regulate its activities, with an emphasis on its interrelation with components of the human carotid atherosclerotic lesion (plaque) which are in constant contact with circulating HDL-associated PON1.

S-glutathionylation in monocyte and macrophage (dys)function

Atherosclerosis is a chronic inflammatory disease involving the accumulation of monocytes and macrophages in the vascular wall. Monocytes and macrophages play a central role in the initiation and progression of atherosclerotic lesion development. Oxidative stress, which occurs when reactive oxygen species (ROS) overwhelm cellular antioxidant systems, contributes to the pathophysiology of many chronic inflammatory diseases, including atherosclerosis. Major targets of ROS are reactive thiols on cysteine residues in proteins, which when oxidized can alter cellular processes, including signaling pathways, metabolic pathways, transcription, and translation. Protein-S-glutathionylation is the process of mixed disulfide formation between glutathione (GSH) and protein thiols. Until recently, protein-S-glutathionylation was associated with increased cellular oxidative stress, but S-glutathionylation of key protein targets has now emerged as a physiologically important redox signaling mechanism, which when dysregulated contributes to a variety of disease processes. In this review, we will explore the role of thiol oxidative stress and protein-S-glutathionylation in monocyte and macrophage dysfunction as a mechanistic link between oxidative stress associated with metabolic disorders and chronic inflammatory diseases, including atherosclerosis.

Association of paraoxonase activity and atherosclerosis in patients with chronic hepatitis B

BACKGROUND

The hepatitis B virus is a significant pathogen that causes cirrhosis, and hepatocellular cancer as a result of the damage it causes to liver cells. Its infection affects more than 400 million people globally. Although there is an effective vaccine and treatment methods, almost 1, 000, 000 people die every year.

OBJECTIVE

To investigate paraoxonase and arylesterase activities along with oxidative status parameters and serum lipid levels, and to find out if there is any increased susceptibility to atherogenesis.

METHODS

Thirty-four subjects with chronic hepatitis B and 39 healthy subjects as control were enrolled in the study. Age, body mass index and gender, Serum Triglycerides (TG), High-density Lipoprotein (HDL) and Low-Density lipoprotein (LDL) levels, serum paraoxonase-1 and arylesterase activities were determined. Oxidative and antioxidative statuses were evaluated by measuring serum-free sulfhydryl groups, lipid hydroperoxide levels, total antioxidant capacity, total oxidant status, and oxidative stress index.

RESULTS

Serum TG and LDL levels were higher while serum HDL levels were lower in patients with chronic hepatitis B than in controls but the differences did not reach statistical significance. Serum paraoxonase-1 and arylesterase activities, plasma free sulfhydryl groups, and total antioxidant capacity were significantly lower in patients than in controls (p=0.018, p=0.005, p<0.001, p=0.037 respectively), while lipid hydroperoxide, total oxidant status, and oxidative stress index were significantly higher (for all p<0.001).

CONCLUSION

The diminution in the paraoxonase-1 and arylesterase activities could contribute to the accelerated development of atherosclerosis in patients with chronic hepatitis B.

Regulation of hepatic paraoxonase-1 expression

Serum paraoxonase-1 (PON1) is a member of the paraoxonases family (PON1, PON2, and PON3). PON1 is synthesized and secreted by the liver, and in circulation it is associated with HDL. PON1 has antioxidative properties, which are associated with the enzyme's capability to decrease oxidative stress in atherosclerotic lesions and to attenuate atherosclerosis development. Epidemiological evidence demonstrates that low PON1 activity is associated with increased risk of cardiovascular events and cardiovascular disease and is an independent risk factor for coronary artery disease. Therefore, pharmacological modulation of PON1 activity or PON1 gene expression could constitute a useful approach for preventing atherosclerosis. A primary determinant of serum PON1 levels is the availability of the enzyme for release by the liver, the principal site of PON1 production. Together with the enzyme secretion rate, enzymatic turnover, and protein stability, the level of PON1 gene expression is a major determinant of PON1 status. This paper summarizes recent progress in understanding the regulation of PON1 expression in hepatocytes.

Paraoxonase 1 in chronic kidney failure

In this review we summarize the findings from the literature and our own laboratory on the decreased PON1 activity in renal failure, the mechanisms proposed and the effect of interventions. In addition to profound alterations in lipoproteins, reduced serum PON1 activity has been clearly established in the past decade and could contribute to accelerated development of atherosclerosis in ESRD and in HD. PON1 lactonase activity is lower in ESRD patients. Hemodialysis partially restores PON1 lactonase and the other activities. PON1 activity recovery after dialysis suggests that uremic toxins may play a mechanistic role in PON1 inactivation. Lower PON1 activity in CRF patients is associated with low thiol concentration, high CRP, and is beneficially enhanced with vitamin C and flavonoids. Changes in HDL subclasses, namely lower HDL₃ in these patients may also play a role in PON1 lower activity. Future research should focus on: (1) mechanistic studies on causes for low PON1 activity and mass; (2) prospective studies focusing on whether there is an added predictive value in measuring PON1 activity (and PON1 activity in HDL₃) in this patient population; (3) intervention studies attempting to increase PON1 activity.

PPARs in Regulation of Paraoxonases: Control of Oxidative Stress and Inflammation Pathways

The paraoxonase (PON) group of enzymes, composed of PON1, PON2, and PON3, play an important role in decreasing oxidative stress by degrading lipid peroxides. PON1 synthesis is upregulated by PPAR. Several pharmacological compounds (acting as antioxidants and, hence, atheroprotective) stimulate both PPAR activity and PON1 expression. Recent evidence suggests that PON1 and the monocyte chemoattractant protein-1 (MCP-1) are involved in coordinating the inflammatory response in damaged tissues; PPAR may be central in the regulation of these biochemical pathways. This article reviews the state of knowledge on PON1 biochemistry and function, the influence of genetic variation, and the regulation of PON1 expression by pharmaceutical compounds that increase PPAR activity. We also describe recent lines of evidence suggesting links between PON1 and MCP-1 and how their production may be regulated by PPAR.

Effect of vitamin e and selenium supplement on paraoxonase-1 activity, oxidized low density lipoprotein and antioxidant defense in diabetic rats

INTRODUCTION

The aim of the present study was to assess the effects of vitamin E and selenium supplementation on serum paraoxonase (PON1) activity, lipid peroxidation and antioxidant defense in streptozotocin-induced diabetic rats.

METHODS

Thirty two female Sprague Dawley rats were divided into 3 groups: the control group (n=8) received a standard diet; streptozotocin (STZ)-induced diabetic rats (n=12), received corn oil and physiological solution; and vitamin E and selenium supplemented diabetic rats (n=12) were treated with oral administration of vitamin E (300 mg/kg) and sodium selenite (0.5 mg/kg) once a day for 4 weeks.

RESULTS

Significantly lower total antioxidant status (TAS), PON1and erythrocyte SOD activities and a higher fasting plasma glucose level were observed in the diabetic rats compared to the control. A significant increase in SOD and GPX activities in vitamin E and selenium supplemented diabetic group was observed after 5 weeks of the experiment. Compared to the normal rats, malondialdehyde (MDA) and oxidized LDL (Ox-LDL) levels were higher in the diabetic animals; however, these values reduced significantly following vitamin E and selenium supplementation.

CONCLUSION

Vitamin E and selenium supplementation in diabetic rats has hypolipidemic, hypoglycemic and antioxidative effects and may slow down the progression of diabetic complications through its protective effect on PON1 activity and lipoproteins oxidation.

Biochemical study of oxidative stress markers in the liver, kidney and heart of high fat diet induced obesity in rats

BACKGROUND

Obesity has become a leading global health problem owing to its strong association with a high incidence of diseases.

AIM

To induce rat obesity using high fat diet (HFD) and to estimate oxidative stress markers in their liver, heart and kidney tissues in order to shed the light on the effect of obesity on these organs.

MATERIALS AND METHODS

Sixty white albino rats weighing 150-200 g were randomly divided into two equal groups; group I: received high fat diet for 16 weeks, and group II (control group): received only normal diet (rat chow) for 16 weeks. Blood samples were taken for measurement of lipid profile, tissue samples from liver, heart and kidney were taken for determination of malondialdehyde (MDA), protein carbonyl (PCO), reduced glutathione (GSH) levels, and the activities of glutathione S- transferase (GST) glutathione peroxidase (GPx), catalase (CAT) and paraoxonase1 (PON1) enzymes.

RESULTS

Data showed that feeding HFD diet significantly increased final body weight and induced a state of dyslipideamia. Also our results showed a significant increase MDA and PCO levels in the hepatic, heart and renal tissues of obese rats, as well as a significant decrease in the activity of GST, GPx and PON 1 enzymes. On the other hand CAT enzyme activity showed significant decrease only in renal tissues of obese rats with non significant difference in hepatic and heart tissues. GSH levels showed significant decrease in both renal and hepatic tissues of obese animals and significant increase in their heart tissues. Correlation studies in obese animals showed a negative correlation between MDA and PCO tissue levels and the activities of GPx, GST and PON1 in all tissues and also with CAT enzyme activity in renal tissues. Also a negative correlation was detected between MDA & PCO tissues levels and GSH levels in both hepatic and renal tissues. While positive correlation was found between them and GSH levels in heart tissues.

CONCLUSION

High fat diet-induced obesity is accompanied by increased hepatic, heart, and renal tissues oxidative stress, which is characterized by reduction in the antioxidant enzymes activities and glutathione levels, that correlate with the increase in MDA and PCO levels in most tissues. This may probably contribute to the additional progression of obesity related problems.

Protein S-glutathiolation: redox-sensitive regulation of protein function

Reversible protein S-glutathiolation has emerged as an important mechanism of post-translational modification. Under basal conditions several proteins remain adducted to glutathione, and physiological glutathiolation of proteins has been shown to regulate protein function. Enzymes that promote glutathiolation (e.g., glutathione-S-transferase-P) or those that remove glutathione from proteins (e.g., glutaredoxin) have been identified. Modification by glutathione has been shown to affect protein catalysis, ligand binding, oligomerization and protein-protein interactions. Conditions associated with oxidative or nitrosative stress, such as ischemia-reperfusion, hypertension and tachycardia increase protein glutathiolation via changes in the glutathione redox status (GSH/GSSG) or through the formation of sulfenic acid (SOH) or nitrosated (SNO) cysteine intermediates. These "activated" thiols promote reversible S-glutathiolation of key proteins involved in cell signaling, energy production, ion transport, and cell death. Hence, S-glutathiolation is ideally suited for integrating and mounting fine-tuned responses to changes in the redox state. S-glutathiolation also provides a temporary glutathione "cap" to protect protein thiols from irreversible oxidation and it could be an important mechanism of protein "encryption" to maintain proteins in a functionally silent state until they are needed during conditions of stress. Current evidence suggests that the glutathiolation-deglutathiolation cycle integrates and interacts with other post-translational mechanisms to regulate signal transduction, metabolism, inflammation, and apoptosis. This article is part of a Special Section entitled "Post-translational Modification."

Vascular protective potential of the total flavanol glycosides from Abacopteris penangiana via modulating nuclear transcription factor-κB signaling pathway and oxidative stress

ETHNOPHARMACOLOGICAL RELEVANCE

"Sanxuelian", the rhizome of Abacopteris penangiana (AP), is traditionally used in Chinese medicine for the treatment of blood circulation stasis, hemorheology barriers, edema and inflammation for patients of metabolic syndrome. This study was to investigate the protective effect of the total flavanol glycosides from AP (FAP) on diabetic vascular impairments by measuring the extents of oxidative stress and inflammatory response in mice.

MATERIALS AND METHODS

The experimental aortic pathology in diabetic mice was induced by fed on high-fat diet and injected with streptozotocin. The activities of FAP on attenuating aortas injuries, hypoglycemic, hypolipidemic, inhibiting oxidative stress and anti-inflammation were investigated. Additionally, the aortic expressions of nuclear transcription factor-κB (NFκB) were determined by western blot and immunohistochemistry analysis. Furthermore, the effects of FAP on human umbilical vein endothelia cells (HUVECs) were studied.

RESULTS

In animal study, the results showed that FAP enhanced the activities of antioxidant enzymes and attenuated the levels of proinflammatory cytokines. The plasma lipid profiles and glucose level in FAP treated groups were significantly decreased along with the vascular impairments were alleviated. Moreover, the aortic expression of NFκB was decreased. In cellular experiment, FAP could inhibit the apoptosis of HUVECs induced by H(2)O(2).

CONCLUSIONS

The results indicated that FAP had hypolipidemic, hypoglycemic and vascular protective activities and represented a potential herb for the treatment of aortic pathology involved with metabolic syndrome.

Human carotid lesion linoleic acid hydroperoxide inhibits paraoxonase 1 (PON1) activity via reaction with PON1 free sulfhydryl cysteine 284

Paraoxonase 1 (PON1) is an HDL-associated lactonase with antiatherogenic properties. These include dampening the oxidation properties of human carotid lesion lipid extract (LLE), which in turn inactivates the enzyme. The aims of this study were to identify the PON1 inhibitor in LLE and explore the mechanism of inhibition. LLE inhibited both recombinant PON1 and HDL-PON1 lactonase activity in a dose- and time-dependent manner. Addition of antioxidants or electrophiles to LLE did not prevent PON1 inhibition. LLE was unable to inhibit a PON1 mutant lacking Cys284, whereas it did inhibit all other PON1 mutants tested. The inhibitor in the LLE was identified as linoleic acid hydroperoxide (LA-OOH) and inhibition was specific to this hydroperoxide. During its inhibition, PON1 acted like a peroxidase enzyme, reducing LA-OOH to LA-hydroxide via its Cys284. A similar reaction occurred with external thiols, such as DDT or cysteine, which also prevented PON1 inhibition and restored enzyme activity after inhibition. Thus, the antiatherogenic properties of HDL could be, at least in part, related to the sulfhydryl-reducing characteristics of its associated PON1, which are further protected and recycled by the sulfhydryl amino acid cysteine.

Serum paraoxonase and arylesterase activities in patients with pulmonary tuberculosis

BACKGROUND

The aim of the present study was to determine serum paraoxonase and arylesterase activities in tuberculosis, nontuberculosis pulmonary disease and healthy subjects.

MATERIALS AND METHODS

In this case-control study we determined the serum paraoxonase and arylesterase activities in 36 patients with pulmonary tuberculosis, 38 nontuberculosis pulmonary disease and 49 healthy controls.

RESULTS

The results showed that serum paraoxonase (PON) activity was significantly lower in patients with pulmonary tuberculosis (61.10±51.62IU/L) than healthy controls (98.79±68.79IU/L) (p<0.05). In addition we found that the level of PON activity was significantly lower in patients with nontuberculosis pulmonary disease (67.49±47.88IU/L) than normal individuals (p<0.05). There was no significant differences regarding PON activity between patients with pulmonary tuberculosis and nontuberculosis pulmonary disease (p>0.05). The arylesterase activity was significantly lower in patients with pulmonary tuberculosis than nontuberculosis pulmonary disease and normal subjects (p<0.05).

DISCUSSION

The lower paraoxonase and aryesterase activities in pulmonary tuberculosis patients compared to healthy subjects might be due to imbalance of oxidant/antioxidant systems in pulmonary tuberculosis patients which needs more clarification.

The Dietary Supplement Protandim Decreases Plasma Osteopontin and Improves Markers of Oxidative Stress in Muscular Dystrophy Mdx Mice

Therapeutic options for Duchenne muscular dystrophy (DMD), the most common and lethal neuromuscular disorder in children, remain elusive. Oxidative damage is implicated as a pertinent factor involved in its pathogenesis. Protandim((R)) is an over-the-counter supplement with the ability to induce antioxidant enzymes. In this study we investigated whether Protandim((R)) provided benefit using surrogate markers and functional measures in the dystrophin-deficient (mdx)mouse model of DMD. Male 3-week-old mdx mice were randomized into two treatment groups: control (receiving standard rodent chow) and Protandim((R))-supplemented standard rodent chow. The diets were continued for 6-week and 6-month studies. The endpoints included the oxidative stress marker thiobarbituric acid-reactive substances (TBARS), plasma osteopontin (OPN), plasma paraoxonase (PON1) activity, H&E histology, gadolinium-enhanced magnetic resonance imaging (MRI) of leg muscle and motor functional measurements. The Protandim((R)) chow diet in mdx mice for 6 months was safe and well tolerated. After 6 months of Protandim((R)), a 48% average decrease in plasma TBARS was seen; 0.92 nmol/mg protein in controls versus 0.48 nmol/mg protein in the Protandim((R)) group (p = .006). At 6 months, plasma OPN was decreased by 57% (p = .001) in the Protandim((R))-treated mice. Protandim((R)) increased the plasma antioxidant enzyme PON1 activity by 35% (p = .018). After 6 months, the mdx mice with Protandim((R)) showed 38% less MRI signal abnormality (p = .07) than mice on control diet. In this 6-month mdx mouse study, Protandim((R)) did not significantly alter motor function nor histological criteria.

Total oxidant status, total antioxidant status, and paraoxonase and arylesterase activities during laparoscopic cholecystectomy

INTRODUCTION

Laparoscopic cholecystectomy is the gold standard for the treatment of gallstone disease; however, adverse hemodynamic changes induced by increased intraabdominal pressure due to pneumoperitoneum are known to occur. Herein, we investigated the effects of pneumoperitoneum on oxidative stress markers, including paraoxonase, arylesterase, total oxidant status, and total antioxidant status, during laparoscopic cholecystectomy.

PATIENTS AND METHODS

Patients that underwent a laparoscopic cholecystectomy were classified as Group I, whereas patients that underwent surgical procedures for an abdominal wall hernia under general anesthesia were classified as Group II. Blood samples were obtained during the preoperative period, the perioperative period, and 24 hours after surgery (postoperative day 1). Leukocyte counts, neutrophil rates, paraoxonase activities, arylesterase activities, and total oxidant and antioxidant status levels were measured.

RESULTS

The differences in leukocyte counts and neutrophil rates were not significant between the two groups. In Group I, no significant differences in the total oxidant and antioxidant status levels were identified; however, paraoxonase and arylesterase levels were lower on postoperative day 1. No significant changes were observed in the total oxidant status, total antioxidant status, and paraoxonase or arylesterase activities in Group II. The perioperative total antioxidant status and arylesterase level were higher in Group I in comparison to Group II.

CONCLUSION

Paraoxonase and arylesterase levels are useful markers in the evaluation of oxidative stress caused by intraabdominal pressure due to pneumoperitoneum.

Paraoxonase 2 is down-regulated by the Pseudomonas aeruginosa quorumsensing signal N-(3-oxododecanoyl)-L-homoserine lactone and attenuates oxidative stress induced by pyocyanin

Two virulence factors produced by Pseudomonas aeruginosa are pyocyanin and N-(3-oxododecanoyl)-L-homoserine lactone (3OC12). Pyocyanin damages host cells by generating ROS (reactive oxygen species). 3OC12 is a quorum-sensing signalling molecule which regulates bacterial gene expression and modulates host immune responses. PON2 (paraoxonase-2) is an esterase that inactivates 3OC12 and potentially attenuates Ps. aeruginosa virulence. Because increased intracellular Ca2+ initiates the degradation of PON2 mRNA and protein and 3OC12 causes increases in cytosolic Ca2+, we hypothesized that 3OC12 would also down-regulate PON2. 3OC12 and the Ca2+ ionophore A23187 caused a rapid cytosolic Ca2+ influx and down-regulated PON2 mRNA, protein and hydrolytic activity in A549 and EA.hy 926 cells. The decrease in PON2 hydrolytic activity was much more extensive and rapid than decreases in protein, suggesting a rapid post-translational mechanism which blocks PON2's hydrolytic activity. The Ca2+ chelator BAPTA/AM [1,2-bis-(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid tetrakis(acetoxymethyl ester)] diminished the ability of 3OC12 to decrease PON2, demonstrating that the effects are mediated by Ca2+. PON2 also has antioxidative properties and we show that it protects cells from pyocyanin-induced oxidative stress. Knockdown of PON2 by transfecting cells with siRNA (small interfering RNA) rendered them more sensitive to, whereas overexpression of PON2 protected cells from, pyocyanin-induced ROS formation. Additionally, 3OC12 potentiated pyocyanin-induced ROS formation, presumably by inactivating PON2. These findings support a key role for PON2 in the defence against Ps. aeruginosa virulence, but also reveal a mechanism by which the bacterium may subvert the protection afforded by PON2.

In vivo administration of BL-3050: highly stable engineered PON1-HDL complexes

Background

Serum paraoxonase (PON1) is a high density lipoprotein (HDL)-associated enzyme involved in organophosphate (OP) degradation and prevention of atherosclerosis. PON1 comprises a potential candidate for in vivo therapeutics, as an anti-atherogenic agent, and for detoxification of pesticides and nerve agents. Because human PON1 exhibits limited stability, engineered, recombinant PON1 (rePON1) variants that were designed for higher reactivity, solubility, stability, and bacterial expression, are candidates for treatment. This work addresses the feasibility of in vivo administration of rePON1, and its HDL complex, as a potentially therapeutic agent dubbed BL-3050.

Methods

For stability studies we applied different challenges related to the in vivo disfunctionalization of HDL and PON1 and tested for inactivation of PON1's activity. We applied acute, repetitive administrations of BL-3050 in mice to assess its toxicity and adverse immune responses. The in vivo efficacy of recombinant PON1 and BL-3050 were tested with an animal model of chlorpyrifos-oxon poisoning.

Results

Inactivation studies show significantly improved in vitro lifespan of the engineered rePON1 relative to human PON1. Significant sequence changes relative to human PON1 might hamper the in vivo applicability of BL-3050 due to adverse immune responses. However, we observed no toxic effects in mice subjected to repetitive administration of BL-3050, suggesting that BL-3050 could be safely used. To further evaluate the activity of BL-3050 in vivo, we applied an animal model that mimics human organophosphate poisoning. In these studies, a significant advantages of rePON1 and BL-3050 (>87.5% survival versus <37.5% in the control groups) was observed. Furthermore, BL-3050 and rePON1 were superior to the conventional treatment of atropine-2-PAM as a prophylactic treatment for OP poisoning.

Conclusion

In vitro and in vivo data described here demonstrate the potential advantages of rePON1 and BL-3050 for treatment of OP toxicity and chronic cardiovascular diseases like atherosclerosis. The in vivo data also suggest that rePON1 and BL-3050 are stable and safe, and could be used for acute, and possibly repeated treatments, with no adverse effects.

Effect of preoperative atorvastatin therapy on paraoxonase activity and oxidative stress after coronary artery bypass grafting

The aim of this study was to examine the influence of preoperative atorvastatin therapy on oxidative stress in coronary artery bypass grafting (CABG) patients. Forty patients who underwent elective CABG were enrolled into the study. Of these patients, 20 received atorvastatin (Group I) for 15 days prior to surgery and 20 patients did not use any antihyperlipidemic agents preoperatively (Group II). Serum paraoxonase 1 (PON1) and arylesterase activities, and total antioxidant status (TAS) and total oxidant status (TOS) were measured before surgery and at 1, 6 and 24 hours after the operation. Paraoxonase 1 and arylesterase activities (p<0.001) and TAS levels (p<0.001 for 1st hour and p<0.05 for 6th hour) in Group II were significantly reduced at the 1 st and 6th hours after the operation, whereas the activities of the enzymes (p<0.01) and TAS levels (p<0.05) were significantly reduced only at the 1st hour after the operation in Group I. The total oxidant status of both groups was significantly increased at the 1 st hour after operation (p<0.05 for Group I and p<0.01 for Group II). In conclusion, 15 days of preoperative atorvastatin therapy does not significantly change either the serum PON1 activity or the oxidative stress after CABG.

Roles of oxidative stress and redox regulation in atherosclerosis

Oxidative stress is believed to be a cause of aging and cardiovascular disorders. In response to inflam-mation or endothelial cell injury, production of reactive oxygen species (ROS) is enhanced in vascular cells. These changes contribute to the initiation of atherosclerosis. Vascular cells possess anti-oxidant systems to protect against oxidative stress, in addition to the redox system. The redox status of pro-tein thiols is important for cellular functions. The Akt signaling pathway exerts effects on survival and apoptosis, and is regulated by the glutathione (GSH)/glutaredoxin (GRX)-dependent redox sys-tem. Sex hormones such as estrogens protect against oxidative stress by protecting the Akt signaling pathway but the physiological role of the extracellular GSH/GRX system has not been clarified, although found an increase in the levels of S-glutathionylated serum proteins in patients with athero-sclerosis obliterans. The results suggested that impaired serum redox potential is a marker of the development vascular dysfunction and estrogen has a possible role in the prevention of atherosclerosis.

Paraoxonase 1 activities and polymorphisms in autism spectrum disorders

Autism spectrum disorders (ASD) comprise a complex and heterogeneous group of conditions of unknown aetiology, characterized by significant disturbances in social, communicative and behavioural functioning. Recent studies suggested a possible implication of the high-density lipoprotein associated esterase/lactonase paraoxonase 1 (PON1) in ASD. In the present study, we aimed at investigating the PON1 status in a group of 50 children with ASD as compared to healthy age and sex matched control participants. We evaluated PON1 bioavailability (i.e. arylesterase activity) and catalytic activity (i.e. paraoxonase activity) in plasma using spectrophotometric methods and the two common polymorphisms in the PON1 coding region (Q192R, L55M) by employing Light Cycler real-time PCR. We found that both PON1 arylesterase and PON1 paraoxonase activities were decreased in autistic patients (respectively, P < 0.001, P < 0.05), but no association with less active variants of the PON1 gene was found. The PON1 phenotype, inferred from the two-dimensional enzyme analysis, had a similar distribution in the ASD group and the control group. In conclusion, both the bioavailability and the catalytic activity of PON1 are impaired in ASD, despite no association with the Q192R and L55M polymorphisms in the PON1 gene and a normal distribution of the PON1 phenotype.

Measurement of serum paraoxonase-1 activity in the evaluation of liver function

Paraoxonase-1 (PON1) is an esterase and lactonase synthesized by the liver and found in the circulation associated with high-density lipoproteins. The physiological function of PON1 seems to be to degrade specific oxidized cholesteryl esters and oxidized phospholipids in lipoproteins and cell membranes. PON1 is, therefore, an antioxidant enzyme. Alterations in circulating PON1 levels have been reported in a variety of diseases involving oxidative stress including chronic liver diseases. Measurement of serum PON1 activity has been proposed as a potential test for the evaluation of liver function. However, this measurement is still restricted to research and has not been extensively applied in routine clinical chemistry laboratories. The reason for this restriction is due to the problem that the substrate commonly used for PON1 measurement, paraoxon, is toxic and unstable. The recent development of new assays with non-toxic substrates makes this proposal closer to a practical development. The present editorial summarizes PON1 biochemistry and function, its involvement with chronic liver impairment, and some aspects related to the measurement of PON1 activity in circulation.

The paraoxonases: role in human diseases and methodological difficulties in measurement

Research into the paraoxonase (PON) gene family has flourished over the past few years. In the 1970s and 1980s, only PON1 was known, and the investigations were conducted, essentially, by toxicologists focusing on protection against organophosphate poisoning. Since then, two new members of the family, PON2 and PON3, have been identified, both being shown to play antioxidant and anti-inflammatory roles. Evidence exists indicating that the PON family is central to a wide variety of human illnesses such as cardiovascular disease, diabetes mellitus, metabolic syndrome, obesity, non-alcoholic steatohepatitis, and several mental disorders. However, research is hampered considerably by the methods currently available to measure the activity of these enzymes. In this review, we summarize the state of knowledge on PON biochemistry and function, the influence of genetic variations, and the involvement of PON in several diseases. The problems associated with PON measurement, such as sample acquisition, lack of reference methods, and variety of substrates, will be presented. Also, we cover some of the present lines of research and propose some others for future progress in this field.

Paraoxonases role in the prevention of cardiovascular diseases

Increased oxidative stress is a characteristic of patients with high risk for atherosclerosis development (hypercholesterolemic, hypertensive, diabetic), and the above phenomenon was shown to be associated with attenuated antioxidative status. The increased oxidative stress in atherosclerotic patients is present in their blood, as well as in their arterial wall cells, including macrophages, the hallmark of foam cells formation during early atherogenesis. Serum high density lipoprotein (HDL)-associated paraoxonase 1 (PON1) reduces oxidative stress in lipoproteins, in macrophages, and in the atherosclerotic lesion, whereas paraoxonase 2 (PON2, which is present in tissues, but not in serum) acts as an antioxidant at the cellular and not humoral level. Both PON1 and PON2 protect against atherosclerosis development, and this phenomenon could be related to their antioxidative properties. The use of nutritional antioxidants such as vitamin E, carotenoids (lycopene and beta-carotene), and mainly polyphenols (such as those present in red wine, licorice root ethanolic extract, or in pomegranate) by atherosclerotic animals and also by cardiovascular patients, leads to a reduction in oxidative stress and to the attenuation of atherosclerosis development. These latter phenomena could be related to the nutritional antioxidants-induced increase in HDL PON1 activity (effects on gene expression, on preventing enzyme inactivation, and on increasing PON1 stability through its binding to HDL), as well as an increase in macrophage PON2 activation (at the gene expression level).

Paraoxonase 1 (PON1) attenuates diabetes development in mice through its antioxidative properties

Paraoxonase 1 (PON1) is a lipo-lactonase which is associated with HDL and possesses antioxidative properties. Diabetes is characterized by increased oxidative stress and by decreased PON1 activity. We aimed to analyze whether oxidative status and PON1 levels in mouse sera and macrophages could affect streptozotocin (STZ)-induced diabetes development. We have used two models of mice under low oxidative stress: STZ-injected apolipoprotein E-deficient mice supplemented with the antioxidant vitamin E, and P47(phox) knockout mice. In both mice models the decreased serum basal oxidative stress, was associated with a decreased rate of diabetes development, compared with control STZ-injected apolipoprotein E-deficient mice or with C57BL mice respectively. These data suggest that oxidative stress accelerates diabetes development. Next, we analyzed the effect of PON1 on macrophage oxidative stress and on diabetes development in STZ-injected C57BL mice, PON1 knockout mice, and PON1 transgenic mice. PON1 overexpression was associated with decreased diabetes-induced macrophage oxidative stress, decreased diabetes development, and decreased mortality, in comparison to C57BL mice, and even more so when compared to PON1KO mice. We thus concluded that on increasing PON1 expression in mice, diabetes development is attenuated, a phenomenon which could be attributed to the antioxidative properties of PON1, as decrement of oxidative stress significantly attenuated STZ-induced diabetes development.

Anti-oxidant and anti-atherogenic properties of liposomal glutathione: Studies in vitro, and in the atherosclerotic apolipoprotein E-deficient mice

Liposomal glutathione, but not the control liposomes (with no glutathione), dose-dependently inhibited copper ion-induced low density lipoprotein (LDL) and HDL oxidation. As peroxidase activity was found to be present in both LDL and HDL, it has contributed to the anti-oxidative effects of liposomal glutathione. In-vitro, no significant effect of liposomal glutathione on J774 A.1 macrophage cell-line oxidative stress and on cellular cholesterol metabolism was observed. In contrast, in the atherosclerotic apolipoprotein E-deficient (E(0)) mice, consumption of liposomal glutathione (12.5 or 50mg/kg/day, for 2 months), but not control liposomes, resulted in a significant reduction in the serum susceptibility to AAPH-induced oxidation by 33%. Liposomal glutathione (50mg/kg/day) consumption also resulted in an increment (by 12%) in the mice peritoneal macrophages (MPM) glutathione content, paralleled by a significant reduction in total cellular lipid peroxides content (by 40%), compared to placebo-treated mice MPM. MPM paraoxonase 2 activity was significantly increased by 27% and by 121%, after liposomal glutathione consumption (12.5 or 50mg/kg/day, respectively). Analyses of cellular cholesterol fluxes revealed that, liposomal glutathione (12.5mg/kg/day) consumption, decreased the extent of oxidized-LDL (Ox-LDL) uptake by 17% and the cellular cholesterol biosynthesis rate, by 34%, and stimulated HDL-induced macrophage cholesterol efflux, by 19%. Most important, a significant reduction in macrophage cholesterol mass (by 24%), and in the atherosclerotic lesion area (by 30%) was noted. We thus conclude that liposomal glutathione possesses anti-oxidative and anti-atherogenic properties towards lipoproteins and macrophages, leading to attenuation of atherosclerosis development.